From the outset, the slow-eating group of 4,192 had a smaller average waist circumference, a mean BMI of 22.3, and fewer obese individuals -- 21.5 percent of the total.

- It's not a race -

By comparison, more than 44 percent of the fast-eating group of 22,070 people, was obese, with a mean BMI of 25.

The team also noted changes in eating speed over the six years, with more than half the trial group reporting an adjustment in one direction or the other.

"The main results indicated that decreases in eating speeds can lead to reductions in obesity and BMI," they found.

Other factors that could help people lose weight, according to the data, included to stop snacking after dinner, and not to eat within two hours of going to bed.

Skipping breakfast did not seem to have any effect.

Limitations of the study included that eating speed and other behaviours were self-reported. There was also no data on how much participants ate, or whether they exercised or not.

Commenting on the research, Simon Cork of Imperial College London said it "confirms what we already believe, that eating slowly is associated with less weight gain than eating quickly."

This may be due to the fact that the satiety signal takes some time to travel from the stomach to the brain, and may arrive only after the fast eater has already consumed more than enough.

But he said that relying on the participants themselves to score whether they eat slowly, or fast, was "considerably subjective" and may skew the data.

Katarina Kos, an obesity researcher from Exeter Medical School, said similar research has to be conducted in non-diabetic people to rule out a potential role for diabetes medication in weight loss or gain.